Examples of a conventional sensor, of a kind as described above, for photoelectrically reading a steering angle include the steering angle sensors illustrated in FIGS. 5 and 6. The steering angle sensor of FIG. 5 is provided, in a casing for a slip ring, for transmitting to a controller the states of various switches provided on a steering pad. The steering angle sensor of FIG. 6 is configured such that a rotating disc called a detecting disc and a sensor for reading the rotating disc are accommodated in a common casing.
In the steering angle sensor illustrated in FIG. 5, a disc 14 having slits 13 formed therethrough for indicating a steering angle is attached, together with a slip ring (not shown), to a position between upper and lower covers 11 and 12 of the slip ring.
A sensor 16 for photoelectrically reading slits 13 and a circuit substrate 17 having circuit parts therefor are housed in an enclosure 15 attached to upper and lower covers 11 and 12.
In operation, slits 13 of disc 14, which rotates with the rotation caused by steering, are read by sensor 16 so that an electronically controlled suspension apparatus can be controlled on the basis of the steering angle detected through the circuit.
In the steering angle sensor illustrated in FIG. 6, a disc, similar to the above described disc 14 of FIG. 5, is housed in a casing 20 provided separately from a slip ring, such as described above, so that the disc can be attached, at a hub 21 thereof, on the steering shaft. A sensor for reading slits of the disc, and circuit parts and a circuit substrate are housed in an enclosure 22 provided at one side of casing 20.
The steering angle sensor illustrated in FIG. 6 detects the steering angle in the same manner as performed by the sensor illustrated FIG. 5, so as to enable electronic control of suspension apparatus on the basis of steering angle.
In either of the foregoing conventional steering angle sensors, the sensor for reading the slits of the disc and enclosure 15 or 22 for housing the circuit of the sensor occupy a large volume at the side of upper and lower casings 11 and 12 or casing 20.
The above described conventional steering angle sensors are therefore disadvantageous in that, as a result of their use, the steering column becomes large and it is difficult to attach levers for light control, for a windshield wiper, etc.